"I'm going to miss seeing him rise to the occasion. Really, when he needed to do something spectacular, he did. That's what I'll miss the most." -Bob Bowman

"I just want to wish him a normal life, which is the most important thing. Life is life. Everyone has ups and downs, but first of all, you have to be a normal human being." -Larisa Latynina, second most-decorated Olympian ever, with 18 of all colours.

"I think I can speak for everyone when I say Michael Phelps will go down as a man who made history. I am happy to have been part of a team with him and it is something I will cherish for the rest of my life. ... Having him not there is going to be really weird." - Ryan Lochte.

"I am not happy that Michael Phelps is retiring. I will race through Rio, but it will not be the same without him." - Laszlo Cseh

"I'm a one-trick pony, and he's the king." - Milorad Cavic

"Congrats to Michael Phelps for breaking the all-time Olympic medal record. You've made your country proud. - bo" - US President Barack Obama in a personal message to Phelps on Twitter.

"He has brought onto the scene so many more people into the sport and it has made people re-think the impossible and re-think what they can do. When someone does that for you, it makes them such an incredible role model." - Missy Franklin, 17.

"He is my hero. I have the 2008 fly final on my laptop in about seven languages. He is definitely the greatest Olympian of all time." - Chad le Clos, who pipped the king by 0.05sec in the 200m butterfly

"I think you can clearly say that by the medal tally he is the most successful. My personal view is that I'm not sure he's the greatest. But he's certainly the most successful." - Sebastian Coe - politician